The present invention pertains to an aircraft tractor without tow-bar, comprising a chassis, which may be divided, and whose front wheel axles are mounted on a front part and whose rear wheel axle stubs are mounted on a rear part. The rear part is forked by a recess for receiving the aircraft's nose wheel landing gear. The rear part is hinged to the front part, if desired, by means of an articulated axle which is parallel to the rear axle. On the front part a lifting paddle is arranged at the front end of the chassis recess, possibly behind the articulated axle, and the lifting paddle has a support surface for lifting the nose wheel landing gear up. The support surface slopes in the rearward and downward direction when the chassis is folded and is horizontal when the chassis is extended. Two mirror-image tow arms are arranged at the rear end of the chassis recess. These tow arms can be moved both from a transverse position for reaching behind each a nose wheel, into a longitudinal position before the nose wheel is picked up into the recess. The tow arms can also move in the forward direction by means of a telescoping rod which is provided with a first hydraulic cylinder-piston unit for adjusting its length. There is at least one nose wheel holder, which is arranged at the front end of the chassis recess, above the lifting paddle. The nose wheel holder can be moved in the rearward direction by means of a third cylinder-piston unit. The lifting device is freely selectable.
In a tractor of this class, which is known from DE-OS/PS 36,16,807, the immobile parts of the two telescoping rods are rigidly attached to the front part of the chassis. The cylinders of the first units, which are located below the associated telescoping rod, are fastened at their ends to the fixed parts of the telescoping rods. The cylinders of the third units are correspondingly attached horizontally to the front part of the chassis.
The disadvantage of this arrangement of the first and third units (to which the second cylinder-piston units for folding and extending the chassis are added), which move the tow arms forward and backward for exerting a counterpressure on the nose wheels in the longitudinal direction of the tractor, is the fact that these four arms, which are designed as roller blocks, are always at a constant height above the support surface of the lifting paddle that is rigidly connected to the front part of the chassis and are consequently closer to each other in pairs in the case of smaller nose wheel diameter and touch the nose wheel associated with them at a point closer to its upper vertex than in the case of a greater nose wheel diameter, which reaches its maximum when the tow arms, on one hand, and the holding arms, on the other hand, are diametrically opposite to one another relative to an approximately horizontal wheel diameter. In the case of an even greater wheel diameter, the grasping and holding arms would come into contact on the lower halves of the wheel, so that they would no longer be able to act as devices for holding down the nose wheels relative to the support surface of the lifting paddle. Consequently, in the prior-art tractor, the nose wheel diameter of the landing gear standing on the lifting paddle determines the degree of reliability with which the nose wheel landing gear of the aircraft to be towed is held down on the support surface.